A high-resolution VLT/FLAMES study of individual stars in the centre of the Fornax dwarf spheroidal galaxy

作者：Letarte B^*; Hill V; Tolstoy E; Jablonka P; Shetrone M; Venn K A; Spite M; Irwin M J; Battaglia G; Helmi A; Primas F; Francois P; Kaufer A; Szeifert T; Arimoto N; Sadakane K

来源：Astronomy & Astrophysics, 2010, 523: A17.

DOI：10.1051/0004-6361/200913413

• stars: abundances
• galaxies: dwarf
• galaxies: evolution
• galaxies: formation
• galaxies: stellar content
• galaxies: individual: Fornax dwarf galaxy

For the first time we show the detailed, late-stage, chemical evolution history of a small nearby dwarf spheroidal galaxy in the Local Group. We present the results of a high-resolution (R similar to 20 000, lambda = 5340-5620; 6120-6701) FLAMES/GIRAFFE abundance study at ESO/VLT of 81 photometrically selected, red giant branch stars in the central 25' of the Fornax dwarf spheroidal galaxy. We also carried out a detailed comparison of the effects of recent developments in abundance analysis (e. g., spherical models vs. plane-parallel) and the automation that is required to efficiently deal with such large data sets. We present abundances of alpha-elements (Mg, Si, Ca, and Ti), iron-peak elements (Fe, Ni, and Cr), and heavy elements (Y, Ba, La, Nd, and Eu). Our sample was randomly selected and is clearly dominated by the younger and more metal-rich component of Fornax, which represents the major fraction of stars in the central region. This means that the majority of our stars are 1-4 Gyr old, and thus represent the end phase of chemical evolution in this system. Our sample of stars has unusually low [alpha/Fe], [Ni/Fe], and [Na/Fe] compared to the Milky Way stellar populations at the same [Fe/H]. The particularly important role of stellar winds from low-metallicity AGB stars in the creation of s-process elements is clearly seen from the high [Ba/Y]. Furthermore, we present evidence of an s-processorigin of Eu.

• 出版日期2010-12
• 单位中国科学院国家天文台